The present invention relates to doors and, more particularly, to an improved bi-fold door assembly.
In recent years, the use of out buildings for storage has expanded to a very significant degree. Such buildings have found use, for instance, as hangers to accommodate the considerable expansion in the use of small aircraft for both business and pleasure with the resulting problem of providing adequate shelter at a reasonable price and for storage of large equipment such as farm machinery, earth moving equipment, large trucks and the like. As a result, the need for large doors for such buildings which operate safely, effectively and efficiently has been the focus of those in this field.
Some years ago, Erect-A-Tube, Inc., our assignee, pioneered the development of a unique bi-fold door. These doors, which are quite large in size ranging to at least 80 feet wide by 20 feet high, have become a standard. It is now recognized that the bi-fold door gives rugged, dependable service and is reliable and easy working even in ice and snow. These doors, which are easy to install on post-frame or steel buildings, can be sheeted and insulated with conventional building materials. As such, the bi-fold doors give extra clearance for large openings and are compatible with all metal building systems.
In the past, bi-fold doors have been adapted to cooperate with vertical door tracks. The door, which includes two parallel door sections which are horizontally hinged, includes means on the bottom of the lower door portions to cooperate with the vertical door track. As a result, the bottom of the door moves straight up from the floor so that snow and ice cannot restrict the opening action in any way thereby reducing the need for snow removal while eliminating frozen door problems.
Despite the numerous significant advantages to a bi-fold door, several problems have remained unresolved. The principal problem has been the difficulty in assuring that the door fully closes when it is lowered so as to provide the requisite security and to fully protect the contents of the building from weather conditions. Because of the vertical door tracks, and the uniqueness of the configuration of the door, the bi-fold door can have a tendency to stick in a partially opened condition.
Another problem with bi-fold doors has been the difficulty in supplying electrical power for automatic openers. This is particularly true for applications such as aircraft hangars located in remote regions or other buildings provided for the storage of construction equipment or other large equipment in areas where there is limited access and difficulty in supplying electrical power. Accordingly, since bi-fold doors are by nature quite heavy, it has been difficult to utilize their many advantages in buildings located in remote regions.
It is therefore an object of the present invention to provide a bi-fold door assembly which takes full advantage of the many features inherent in prior bi-fold door constructions while overcoming the few remaining obstacles to perfecting the design, construction and operation of such doors.
These and other objects, features and advantages of the present invention will become apparent from the following description when considered in connection with the accompanying drawings.